is the points on unit circle, at angle , here is a visualization of how such circle is derived from the sum of power series:

Assume we have a function with the property of its derivative is equal to itself, just as , such function should have the form:

Expand to complex number :

Draw these complex numbers as vectors on complex plane, we have a end point for each , and a unit circle with all s

```
function drawETheta(theta, iter, scale) {
var itheta = new Complex(0, theta);
var res = new Complex(1, 0).add(itheta);
var path = new Path();
path.strokeColor = 'black';
path.add(origin);
path.add(cord(new Complex(1, 0) * scale));
var itheta_pow = new Complex(itheta);
for (var i = 2; i < iter; i++) {
path.add(cord(res * scale));
itheta_pow = itheta_pow.multiply(itheta);
res = res.add(itheta_pow.divide(factorial(i)));
path.add(cord(res * scale));
}
return path;
}
```